Disclosure to Promote the Right To Information

Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public.

इंटरनेट मानक

“!ान $ एक न' भारत का +नम-ण”Satyanarayan Gangaram Pitroda

“Invent a New India Using Knowledge”

“प0रा1 को छोड न' 5 तरफ”Jawaharlal Nehru

“Step Out From the Old to the New”

“जान1 का अ+धकार, जी1 का अ+धकार”Mazdoor Kisan Shakti Sangathan

“The Right to Information, The Right to Live”

“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता है”Bhartṛhari—Nītiśatakam

“Knowledge is such a treasure which cannot be stolen”

“Invent a New India Using Knowledge”

है”ह”ह

IS 7662-1 (1974): Recommendations for orientation ofbuildings, Part 1: Non-industrial buildings [CED 12:Functional Requirements in Buildings]

f

18 : 7662 (Part I) - 1974

Indian Standard RECOMMENDATIONS FOR

ORIENTATION OF BUILDINGS PART I NONINDUSTRIAL BUILDINGS

(Third Reprint MARCH 1996 )

UDC 721.011.22

0 Copyright 1975

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

Gr 5 September 1975

EJ : 7662 (Part I) - 1974

Indian Standard RECOMMENDATIONS FOR

ORIENTATION OF BUILDINGS PART I NONINDUSTRIAL BUILDINGS

Functional Requirements in Buildings Sectional Committee, BDC 12

Chairman Representing *LT-GEN B. N. DAS Ministry of Defence

Members ADDITIONAL DIRECTOR STANDARDS

(ARCHITECTURE) DIRECTOR (ARCHITECTURE) SIIRSMATI E. S. GHUMAN SHRI J. C. KAPUR S~IRI B. D. KSHIRSA~AR

SHRI L. R. LALLA (Alternate) SHRI G. C. MATHUR DR V. NARA~SIMHAN

Ministry of Railways

Central Public Works Department Indian Institute of Architects, Bombay Danfoss (India) Ltd, New Delhi Ministry of Defence

National Buildings Organization, New Delhi Central Building Research Institute (CSIR):

Roorkee SHRI M. R. SHARYA (Alternate)

SHRI J. R. OVALEKAR SHRI N. RAGHAVAN (Allcrnate)

SHRI M. M. PANDE DR P. S. PANT SHRI R. N.. PAWAK SHRI R. 1,. PURI SHRI S. PURSHOTUA>~A

National Safety Council, Bombay

Voltas Ltd, Bombay Directorate General of Observatories, New Delhi Directorate General of Health Services, New Delhi In personalcapacity (A-116 Vasant Vihar, New Delhi) Ministry of Lahour, Employment Pr Rehabilitation,

PROP RATTAX KUMA~ SHR1 S. SUBBA RAO

New Delhi University of Roorkee All India Institute of Hygiene & Public Health,

Calcutta . SHRI A. V. RAO (Alternate)

SHR1 S.4YF.D S. SHAPI SHRI D. P. SHARMA (Altexate)

SHRI D. AJITUA SIMHA, Director (Civ Engg)

Institute of Town Planners, New Delhi

Director General, ISI (Ex-o&‘o Member)

Secretary SHRI V. KALYANASUNDARAM

Assistant Director (Civ Engg), IS1

(Confinued on page 2)

*Lt-Gen B. N. Das also represents The Institution of Engineers (India), Calcutta.

0 Cotwright 1975 BUREAU OF INDIAN STANDARDS

This publication is protected under the Indian Copyright Act (XIV of 1957) and reproduction in whole or in part by any means except with written permission of the publisher shall be deemed to be an infringement of copyright under the said Act

Is: 7uz2 (PartI)-

(-frm pa% 1)

Orientation and Ventilation Subcommittee, BDC 12 : 4

CoIIvmr SHRl b%. v. SATHE

M&S

DIRECTOR (ARCHITECTURE) Lomb DxR~~~ToR STANDARDS

w-tins Ministry of Defence

Central Public Works Department Ministry of Railways

- (ARCHITECTURE) SHRX A. P. RANVINDE M/s Kanvinde 8s Rai, New Delhi SHRI M. M. Msr~v National Buildings Organization, New Delhi Smu M. M. PANDE SHR~ R. S. PANEZAR

Voltas.Ltd, Bombay Coun~,;lf Sctenttfic & Industrial Research, New

DR P. S. PANT Directorate General of Observatories, New Delhi SHRI S. PURSHOTH~~~A Minii of Labour, Employment and Rehabilita-

tion, New Delhi SHRI hi. R. SHARMA fknt;!ar~ilding Research Institute (CSIR),

SHRI ISHWAR CHAND (Al&ma&)

IS : 7662(PartI)-lW4

Indian Standard RECOMMENDATIONS FOR

ORIENTATION OF BUILDINGS

PART I NONJNDUSTRIAL BUILDINGS

0. FOREWORD

0.1 This Indian Standard (Part I) was adopted by the Indian Standards Institution on 9 December 1974, after the draft finalized by the Functional Requirements in Buildings Sectional Committee had been approved by the Civil Engineering Division Council. . 0.2 The chief aim of orientation of buildings is to provide, physically ‘and psychologically comfortable living inside the buildings by creating conditions which suitably and successfully ward off the undesirable effects of severe weather; complete elimination of such undesirable situations may not be possible but with judicious use of the recommendations and knowledge of climatological factors, the ill effects can be reduced to a considerable extent.

0.3 Climatological factors are the most importaut of all factors which would normally help in deciding the orientation. However, in each individual case, ideal/desirable orientation may not be possible due to various other factors in a given situation. Fortunately however, in such cases, due to recent advances in types of constructions and materials and mechanical aids for lighting and ventilation, near idcal conditions can bc achicvcd for living and work.

0.4 The Sectional Committee noted that work on thermal stress index for indoor summer conditions for people acclimatized in different parts of the country has been in progress in Central Building Research Institute, Roorkec. It was decided to inch& suitable data in this respect as soon as these arc available.

0.5 Part II of this standard will deal with the orieutation of industrial buildings.

0.6 In the preparation of this standard assistance has been drawn from the following publications :

Building Digest 74. Central Building Research Institute, Roorkec.

Climatological and solar data for India. Central Building Rcscarch Institute, Roorkcc.

3

Is : 7662(PartI)-1974

Ford Foundations Report on climatic evaluation and architectural recommendations for the region of Delhi.

Overseas Building Notes No. 71. Some principles of design for warm climates. Overseas Division, Building Research Establishment, England.

Overseas Buildings Notes No. 117. Nontraditional buildings for warm climates. Overseas Division, Building Research Establishment, England.

Technical information series. Climatic data for design of buildings. National Buildings Organization, New Delhi.

0.7 For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS : 2-1960*. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.

1. SCOPE

1.1 This standard (Part I) covers general principles and relevant factors which help to decide orientation of nonindustrial buildings.

2. TERMINOLOGY

2.0 For the purpose of this standard, the following terms shall apply.

2 .l Cloud Coverage - The cloud coverage of sky is indicated in the mrteorological data in the form of coverage of ‘tenths of sky’ by ‘all clouds and ‘low clouds’. It is given in the form of tables for each month.

2.2 Relative Humidity - The ratio of‘the actual partial pressure of the water vapour in the air to the saturation pressure of water vapour at the same Lemperalurc.

2.3 Solar Loads - Direct solar radiation on roof and on vertical faces of diffcrcntly oriented walls on clear days are given in the form of tables and graphs. They help to study the amount of heat received by the walls and roof of a building due to solar radiation.

2.4 Sun Charts - Sun charts indicate the diurnal path of the sun giving the points of its horizontal (azimuth) and vertical (altitude) locations in the Fky at a particular hour of a particular month of a region.

2.5 Temperature -. The means of daily maximum and minimum tempera- tures are given in the form of tables or isopleths for a particular region for a year or for different months for the country as a whole.

*Rules for rounding off numerical values (&.wd).

4

IS : 7662 (Part I) - 1974

3. CLIMATOLOGICAL FACTORS

3.1 The following climatological factors which influence the optimum orientation of a building shall be taken into account :

a) Solar radiation and temperature, b) Clouds and rains, c) Humidity, and d) Prevailing winds.

3.2 Solar Radiation and Temperature 3.2.1 The solar radiation is present during the day only. The normal

practice has been to work during day and to rest during night. The two functions of work and rest are distinct. A residential building houses both , the functions. But there are a number of buildings which are meant pri- marily for work. Working for twenty-four hours with shifts has also come to stay, but in many cases it would be adequate to orient buildings after taking into account climatological factors of the day only. Where work round the clock is carried on, both for working and comfort, mechanical aids in lighting and/or ventilation are called for during night. There is therefore likely to be no special problem for night in relation to orientation.

3.2.2 The climatological factors of day and night shall, however, be studied. To some extent this would help in deciding variations in orientation of buildings by taking into account the hours of work as well as the functions either of work and/or rest.

3.2.3 The temperature and solar radiation are related. The intensity of solar radiation depends on the direction of the sun’s rays. The sun’s radiation has the effect of both warming as well as creating glare. The question of glare has not been’considered in detail here as it has been dealt with separately in IS : 2440-1968*. It may, however, be noted that this is an important factor and protection from it is necessary for comfort. The problem of glare arises due to the sun’s radiation but measures taken against that radiation do not necessarily solve it. The field of glare is very wide. The important factors producing glare are the bright sky and the surround- ing areas. But it is principally felt due to violent contrast and not due to total intensity of light or radiation. These factors affect all the sides irrespec- tive of the sun’s radiation which may vary and which may be practically absent on one side, as for example, on the north in winter. Glare may be reduced by screens and Venetians or by plantations and colour treatments to the source of glare.

3.2.4 The effect of warming by the sun’s radiation is experienced by rise in temperature. The temperature of a structure and living space is raised : (a) directly by the penetration of the sun’s rays through openings, and (b) indirectly through the absorption and radiation of heat by the walling

*Code of practice for daylighting of buildings (Jfrst r&-ion ).

5

and roofing materials. For comfortable living at least during the summel both the factors should be considered. Thus, measures adopted to shiel, direct penetration of the sun’s rays through openings would not be useful . the adjacent walls and roofs do not have sufficient insulation value. Rot is the most affected part of the structure because it receives direct sun’s ray throughout the day, both in summer and winter. The treatment of rot should, therefore, receive adequate attention for creating comfort in building: The four sides of the buildings should be considered individually and collec tively (see 3.2.5). The easiest method of providing comfort through orient; tion is to avoid aspects which raises the temperature inside the building eithe by eliminating the penetration of the sun’s rays or by providing an envelop of shade over as large a part of the building as possible. In case of co1 climates exactly the reverse considerations will prevail due to the need fc maximum warmth and the sun.

3.2.5 The different facades of a building have some inherent characteristic from solar point of view which can be utilized with advantage by a prope understanding of those characteristics. For instance, a south facade has th advantage of receiving much larger solar radiation during winter than tha during summer. Even for openings on the south facade, a small overhan oan cut off direct solar penetration during summer and allow it during winter This, obviously, is the most advantageous aspect, not available on any othe facade.

3.2.5.1 For the most parts of the country north of 23”N latitude, the SUJ does not shine directly on the north facade, except during early morning or late afternoons in summer. Even on other latitudes south of 23”N, th sunlight at mid-day during summer, in addition, comes from a very higl altitude sun. It is much easier to effectively cut off the early morning am late afternoon sun on this facade by vertical louvers on either side of th opening and the mid-day sun south of 23”N, by a small overhang on top A larger south facade necessarily implies an equal north facade and hot1 together can be utilized advantageously throughout the year.

3.2.5.2 The eastern and western facades receive nearly equal amount of daily solar radiation throughout the year. The only difference is tha when the sun shines on the eastern facade, the building is comparativcl: cool after a cool night and the air temperature is also low. So the solar hca through this facade is not so pronounced indoors unless, of course, the easterr facade is all unshaded glass area. On the other hand, western facade cn counters a different situation. Due to the higher air temperature in the afternoon, the heat flow indoors is further augmented by the incidence o solar radiation on the western facade. This heat can be minimized b) reducing the western facade or by providing thermal insulation on the exterior or by shading this facade by verandahs, creepers, plants, etc.

33.6 The best orientation from a solar point of view requires that the building, as a whole, should receive the maximum solar radiation in winter

6 ;

IS : 7662 (Part I) - 1974

and the minimum in summer. For practical evaluation, it is necessary to know the duration of sunshine, and hourly solar intensity on the various external surfaces on representative days of the seasons. The total dir&t diurnal solar loads per unit area on different vertical surfaces are give9 in Table 1 for two days in the year, that is, 16 May and 22 December, re- presentative of summer and winter, for latitudes corresponding to some important cities all over India. From Table 1, the total heat intake can be calculated for all possible orientations of the building for the extreme days of summer and winter.

TABLE 1 DAILY TOTAL DIRECT SOLAR RADIATION ON VERTICAL SURFACES IN g.caX/cms/DAY FOR TWO REPRESENTA!IYVE DAYS

(Clausts 3.2.6 and B-1.3)

19’N 23”N 29”N

D rMay 22 16 22 16 22 16 22

North 187 North east %-! 35 :“;o 27

83 :z -ii Iii ii

46 -9

East 187 232 173 157 247 South east 100 291 115 294 141 158

:z ;;

126 281

south - 358 south west loo 291 1%

377 % 398 64 294 1% 295

1:: 297

ii!

West 225 187 232 173 240 157 247 :!!

North west 228 35 214 27 194 20 188 ‘E 180 12Z

3.2.6.1 The method of calculating solar load on vertical surfaces of different orientations is given in Appendix A.

3.2.6.2 An exatiple to illustrate how to work out on orientation of a building from the solar point of view is given in Appendix B.

3.2.7 In order to ascertain good and bad aspects and to decide whether or not to take advantage of the sun’s rays, day and night temperatures of the region, for which orientation is to be decided, should be studied in rela- tion to the following broad classifications of temperatur; ranges (see also 3) :

Below 15°C 15 lo 20°C

Cold Cool

Sun’s rays advantageous

20 to 30°C Temperate 30 to 35°C Hot Protection from sun’s rays Above 35°C Very Hot advantageous

3.2.8 When the mean maximum temperaturq during the day are of cool category or below it, it would be necessary to take the benefit of the sun’s rays. As a rule such low day temperatures occur in winter between months of November and February. The movement of sun (between rise and set) during this period is invariably from E.S.E. to W.S.W. and its altitude is

7

IS : 7662 (Part I) - 1974

also low compared to summex months. This suggests that a south aspect would always be better than others for taking advantage of the sun in regions where it would be necessary to take it.

3.2.9 When mean maximum day temperatures fall within the limits of 20” to 30°C (temperate) the problem of orientation of building would be influenced more by considerations other than the radiation of sun such as glare, humidity, prevailing winds, view, etc, which are being dealt with sepa- rately under relevant headings.

3.2.10 In regions where mean maximum temperatures rise above 30°C (hot and very hot), high temperatures occur in the months of April to June and always between 2.0 and 5.0 P.M. The position of the sun during these hours of the day would invariably be towards the west. The exact location would vary from west to W.S.W. in latitudes higher than 20”N and from W.N.W. to west in latitude lower than 20”N. Therefore, in the northern plains of India, the west and W.S.W. aspects become worse. The altitude of sun is also low at these hours and it is difficult to devise simple and efficient methods of sun protection on the west aspect. During noon, solar radiation on a horizontal surface is maximum and air temperature is also pretty high. The sun shines on north/south walls from a high altitude and it is easy to protect these walls against solar radiation incidence by merely providing a small horizontal projection; small horizontal projection on walls would cast long shadows when the sun is at a high altitude. It is a popular belief that south aspect is bad in summer but it should be noted that in northern India during summer, the south wall receives the least solar radiation. In fact, the incidence of ground reflected radiation on the human body from a southernly sun in a south facade causes greater thermal discomfort and visual glare. To minimize the reflected solar heat suitable nonreflective and absorptive’ surfaces as for example, grassy lawns should be developed in front of the south facade.

3.2.11 The diurnal range of temperatures also gives important clues to the type of climate of a locality. A large difference (8°C or more) between the daily mean maximum and minimum temperatures would suggest a dry climate and if the maximum temperature extends to above 30°C the condi- tions would be hot and dry. In such a climate, protection of openings against direct incidence of sunlight indoor is very essential; evaporative cooling brings great relief; roof spray proves very helpful. On the other hand if the daily mean maximum temperature extends to above 30°C but the diurnal range between the daily mean maximum and minimum tempera- tures remains below 8°C the conditions signify a hot humid climate and in this climate, maximum relief is obtained only by the provision of profuse ventilation through large openings in opposite walls facing the prevailing wind direction.

3.3 Clouds and Rains

3.3.1 The other climatological factors are more important than clouds

8

L

IS : 7662 (Part I) - 1974

and rain but the clouds not only reduce the direct radiation but also make ineffective the devices of sun protection. It is, therefore, more convenient to take note of cloudy periods of the year and if they coincide with hot periods, then, the ideas of sun protection should be given up although high temperatures may demand stich protection.

3.3.1.1 The meteorological data regarding clouds is given under three broad types ‘low’, ‘medium’ and ‘high’. Low clouds are those whose heights of base vary from very low levels up to 2 500 metres. The amount by which low clouds cover the sky largely determines the effect of both incoming solar radiations and outgoing terrestial radiation.

3.3.2 The direction of the rain is generally the same as that of the pre- vailing wind except in case of storms. If the buildings are oriented ‘to take such prevailing winds, special precautions and devices would be necessary to prevent rains beating into the buildings.

3.4 Humidity

3.4.1 In hot periods, the human body gives out moisture by way of perspiration to regulate its temperature. There is no discomfort as long as there is scope for absorption of such moisture in the air. Where there is no such absorption, the air around the body gets saturated with the moisture and gives rise to a sensation of discomfort. Movement of air during such conditions removes saturated air from the vicinity of the body and brings fresh air into its contact. This gives a relief although there may not be any change in room temperature. Due to this reason, movement of air and the use of prevailing wind are very important during periods of high humidity.

3.4.2 The discomfort due to high humidity can be counteracted, to a great extent, rith electric fans or mechanical ventilation. In the past as solar radiation was largely counteracted with heavy construction and surrounding verandahs, there was apparently an over-emphasis on humidity and prevailing winds. . With the introduction of electric fan to effectively counteract humidity and taking into account the rise in costs of construction, perhaps, it would be better to shift the emphasis on solar radiation where temperatures are very high. When there is less diurnal variation between mean morning and mean maximum temperatures alongwith high humidity, the emphasis should be on humidity and prevailing winds.

3.4.3 A comparative study of relative humidity can be made under following categories :

O-25 percent 25-50 ,, 50-75 ,,

Ey dry Humid

75-100 ,, Very humid

3.4.4 When humidity is:f the category of ‘dry’ and ‘very dry’ it is easy to take its advantage by evaporative cooling in summers; when it is ‘humid’

9

L- ,-.. ~.-1~^_^.~.-1_-_~__._-..- .__--___,___._ .._

._

16 : 7662 (Part I) - 1974

or ‘very humid’ it is desirable to regulate the rate of air movement either artificially \vith the aid of electric fans or with the help of prevailing winds.

3.4.5 Comfort in relation to humidity becomes complex. nuring humid period one can feel very warm when the air temperature is 30°C and condi- lions calm. One may, however, feel cool even if temperature rises to 32°C and there is little breeze. It will 1~ quite cool at the same temperature if there is reduction in the relative humidity and if there is breeze.

3.4.6 For assuring comfort in humid regions, the temperatures within the buildings should be kept as near as possible to the shade temperature by USC of: (a) fans and forced ventilation to achieve speedy air movement up to 50-100 cm/s, (b) adopting light weight construction of low thermal capacity, (c) using materials externally with low absorption capacity for heat, etc, and (d) by minimizing the effect of solar radiation.

3.5 Prevailing Winds 3.5.1 The prevailing wind helps to create natural ventilation in a building

to provide comfort during the periods of high humidity.

3.5.2 With judicious location of rooms inside a building and with location of suitable windows at proper points in the rooms, desirable wind movement indoors and the requisite ventilation can be ensured. For comfort it is also necessary that air movement should occur in building at the level of occupances and use.

3.5.2.1 Where there is extreme heat in summer and where it is necessary to close openings to avoid heat and glare it would be an advantage to orient buildings to face the winds of the humid months instead of average prevailing wind which may be from some other direction.

3.5.2.2 Where appropriate, reference shall be made to IS : 3362-1965*.

3.5.3 Where there are rows of buildings, wind eddies are produced on the leeward side. The field of eddies is determined by the height, length and width of building blocks. Prevailing wind becomes weak and indefinite in the field of eddies and cannot produce adequate natural ventilation in build- ings located in such areas.

3.5.4 It is not necessary to face the buildings directly into prevailing winds because their velocity is not reduced considerably by facing the building away even up to 30”.

3.5.5 Specific consideration should be given to strong hot and cold winds in regions where they are present.

3.5.6 For the and direction P

urpose of orientation, it is necessary to study the velocity oft le wind at each hour and each month instead of relying on

generalizations of a month or a period or for the year as a whole. This helps to spot the right winds for particular period of day or night.

*Code of practice for natural ventilation of residential buildings.

10

IS : 7662 (Part I) - 1974

4. BASIC DATA

4.1 The climatological factors necessary for the determination of orientation of buildings are available in the form of basic data, such as sun charts, solar loads, temperature, cloud coverage of the sky, relative humidity and winds.

4.1.1 Basic data available in publications of Meteorological Department; ‘Climatological and solar data for India’ issued by the Central Building Research Institute, Roorkee; and ‘Climatic data for design of buildings - Technical Information Series’ issued by the National Buildings Organisation may be seen.

4.1.2 Since the data given in 4.1.1 is on an average basis it would not cover special situations in the country, such as occurrence of severe hot or cold winds during some months in a year in places near desert areas. In such cases, it is necessary to obtain more climatological details for deter- mination of a suitable orientation.

5. BASIC ZONES AND THBIR PROBLEMS 5.1 The study of climatological factors helps to divide India into suitable zones. In IS: 3792-1966* four zones have been indicated with regard to heat insulation. This standard may be referred to for more information and details.

5.2 For the purpose of orientation it would, however, be more convenient to divide the country in three broad zones :

a) Hot and arid, b) Hot/warm and humid, and c) Cold.

5.2.1 It is to be remembered that there may not be uniform climatic fac- tors in a particular zone. same zonal region.

They might even vary during day and night in the Each zone, all the same, poses certain basic problems.

These problems call for solutions. Reference to each zone has been made separately in 5.3 to 5.6.

5.3 The main problem of the hot and arid zone is to keep out the day time heat or the solar radiation. Past methods of shading the openings with CHAJJAS, thick walls with small openings, more height and deep verandahs do help in creating certain level of comfort; though except for provision of CHAJJAS, the other methods will prove uneconomical in the present day circumstances. Ultimately the most effective method will be the right ori- entation. More height does not improve ventilation. Ventilation depends on air intake rather than on the volume of room. Verandahs on the east and west are not very effective because of the general low altitude of sun on these sides. For sleeping purposes also, verandahs are not always satisfactory

*Guide for heat insulation of non-industrial buildings.

11

IS : 7662 (Part I) - 1974

because of the radiation given out at night by their floor and the surrounding masonry. In single/double starey development coin-tyards ofi:r physical and psychological advantages provided that they are shaded during day, lantl- srapcd properly and cooled by sprinkling water. Tn multistorcy dcvclop- ment, however, terraces, staggered balcony, etc, have: to be rcsortc,d to in order to achieve this end.

5.3.1 In hot and arid zone, walls and rools should have adequate thermal capacity and time-lag. Sunlit surfaces, and not just openings should 1~: rcflectivc and/or be heavily shaded. Air movement should, as a rule, IX rcstrictcd to the minimum required for ventilation. But fresh air is very useful during the evening to counteract the heat gained by the structure which, by the evening, would bc radiated to the interior.

5.3.2 Summer nights arc very uncomfortable in this zone. Interiors arc unbearable as surrounding walls and roof radiate thermal heat stored by them during the day. Terraces, open verandahs, staggcrcd sleeping out balconies and structures enclosed with light construction and materials which give: up heat quickly are necessary for comfortable sleep at night.

5.4 The main problem of hot/warm and humid zone is to provide maximum of ventilation, natural if possible, to counteract discomfort of humidity. It is simple to increase humidity but it is not at all possible to reduce it by any economical method. The best solution is, therefore, to make maximutn use of preva.iling winds. Glare is also generally present in this zone. Screens and JALLIES are more effective as they not only screen bright sky but also allow breeze to pass through them.

5.4.1 In the hot/warm and humid zone the effort should he to maintain indoor temperatures, as near as possible, to the ambient or shade temperature. Walls and rools, if possible, should be of light weight construction having low thermal cdpacity. The external surface should absorb as little solar radiation as possible and the internal surface should emit minimum of long wave radiation. *Air movement should normally he speedy up to SO-100 cm/s, which may have to he obtained artificially if prevailing winds do not help to do so.

5.5 The problems of the cold zone are that during summer if the sun’s radiation is excessive, there should be some shading during day hut at night both in summer and winter cold air should be shut out. Uuring day, in winter, sunshine should bc wclcomc.

5.5.1 In thr cold zone, cspccially in hills, walls and roofs should be heavy weight with high thermal capacity for absorbing and storing heat during day and using the stored heat to warm the inside of the building during the night. If heavy weight roofs arc not feasible, they should be insulated against loss of the heat of the interior during night. Air movement and ventilation should be rcstrictcd to the minimum. Kegular flues or devices for minimal perma- nrnt ventilation at night should bc provided to avoid concentration of carbon

12

fS : 7662 (Part I) - 1974

monoxide when open coal fires are used for heating in enclosed rooms, in winter, especially m hiIl town.

5.6 The main zonal factors and an appreciation of their problems cannot suggest orientation suitable to the whole area covered by different zones. For the orientation of a place, city or town., its climatological, topographical and other related factors should be studied m detail in the manner prescribed in this standard, to decide an optimum orientation.

6. INFLUENCE OF LAYOUTS AND ROAD SYSTEMS

6.1 Often layouts and road systems in them predetermine orientation of individual or group of buildings, it is therefore necessary to consider steps to minimize their handicaps and to suggest methods of assuring better orienta- tion in case of fresh planning.

6.2 In a city or a town where building sites and road patterns are fixed, practically no choice is left for orientation. When the abutting road dots not allow desirable orientation, insistence by bye-laws or otherwise, for facing the building on that road should be relaxed. At least on large plots, whcrc buildings are detached, there should be no restriction to the siting of the build- ing to achieve optimum benchts of orientation. An approach road at one side would help the building to face on that side instead of the statutory road. This should be acceptable because the present trend is to design all the four elevations properly and if so any one of them can face the statutory road without sacrificing public interest civic or aesthetic.

6.3 Statutory building liucs which are parallel to the road sometimes force. undesirable orienmtion to buildings. This can be improved by allowing to keep building bees at au appropriate angle to the road. If such faring is uniform throughout the street, it would not handicap harmony of SIIXY~I architccturc which is the aim of enforcing building lines. While stipulating building lines, oricutation aspect of the proposed development should bc kept in mind, instrad of following ‘parallel to the road’ approach.

6.4 Fresh plauning of layouts and neighbourhoods should incorporate road patterns which enable desirable/good orientation to the maximum number 01 blocks.

6.5 The heights and dcpthy of building blocks and the width ofstrccts which decide the distance between the blocks, should be such that, in addition to providing adequate air, light and means of communications, each building may have access to natural winds or at least to those winds which are most us&l either directly or through systematic channelizing. When a row of buildings faces directly against the wind, they block the flow of wind to other rows. If the blocks are oriented oblique to the wind direction and il’gaps arc provided between them, the obstruction to winds is lessened considerably.

6.6 Particular attention should be paid to the layout of terrace houses because they receive light and air from two sides only. For such housing,

IS : 7662 (Part I) - 1974

6.7 J'JilJIliJJJ: 01 Ircth ill ~Il’cC:(5 ;lllCI ill OjJ’:Jl bJJi%(.C> >Ilf,llIll I,r ClOJlC: ( ilJt:fllIIy

lo take ;ulv:t~Jl;~ge bcnlr 01 slracle~ :lJld huJciiJiJJc without ll;~~~~iic.al~l~iJ~~ 11~ fk,V< ol’Jli,tlll~~Ll WillI!!>. ‘1’1 IC*iJ’ iJ(tV%llti&C fi,J’ ;llJiltiJlp gh’c: allti fo1’ JJr(JVidiIlg UN,/

irll(I/c,t’ W~II’JII [J<~(;j\c:l~ ill ~lcv~*l<lJed arcas hllfJU]d z.~ILIJ I,I: IakCJJ. ,SOJIlC 1I‘cc’:

>lic*tl It-;lvc:\ ill wiJttc:r wllilt: retain tlJick fibliagc in suJJnJJ(:J.. Such 11~s will bc very advaJJtagcous particularly where southern and \vcstcrn exposures arc concerned; by allcwing maximum sun during winter aJJd cflcctively blocking it in summer.

APPENDIX A (Clause 3.2.6.1)

METHOD OF CALCULATING SOLAR LOAD ON VERTICAL SURFACES OF D IFFERENT ORIENTATION

A-l. DETAILS OF CALCULATION

A-l.1 The solar energy above the earth’s atmosphere is constant and the amount incident on unit area normal to sun’s rays is called solar constant (2 g/cal/cma/min). This energy in reaching the earth’s surface, is depicted in the atmosphere due to scattering by air molecules, water vapour, dust parti- cles, etc, and absorption by water vapour and ozone. The depletion varies with varying atmospheric conditions. Another importaJJt cause of depiction is the length of path traversed by the sun’s rays through the atJnosphere. This path is the shortest when the sun is at the zenith and, as the altitude of the sun decreases, the length of path in the atmosphere incrcascs. l’igurc I gives the computed incident solar energy/hour on unit surface area normal to the rays under standard atmospheric conditions * for different altitudes of the sun.

A-l.2 In order to calculate the solar energy 011 any surf~rcc other 111aJl JJormal to .the rays the altitude of the sun at that timcf should be known. The corresponding value of direct solar radiation (Zdv) should then bc found out with the help of Fig. 1. The solar radiatioJ1 incidellt on any surface (Is) is given by :

Is=& (Sin /I Sin $+Cos /3 Cos 4 Cos 95)

where fl = solar altitude, $ = angle tilt of the surface from the vertical (see Fig. 2), and oc = ,wall solar azimuth angle.

*The standard atmospheric conditions assumed for this computation are: cloud-free, 300 dust particks per ems, 15 mm of prccipilable water, 2.5 mm of ozone. al sea lc~cl.

tThcsc are given for every hour at different latitudes in ‘Climatological and solar data for India’ published by the Central Building Research Institute, Roorkee.

14

90

80

10

0

EC1 SOLAR RADIATI NORMAL TO SUN

.lO 20 30 LO 50 60 70

SOLAR ALTITUDE-DEGREES

FIG. 1 DIRECT SOLAR INTENZXTIES NORMAL TO SUN AT FOR STANDARD CONDITIONS (COMPUTED)

80 90

SEA LF;vEL

FIG. 2 DEFINITION OF SOLAR ANGLES 15

IS s 7662 (Part I) - 1974

APPENDIX B

(Clause 3.2.6.2)

AN EXAMPLE TO FIND OUT ORIENTATION ON THE BASIS OF SOLAR LOAD

El. EXAMPLE

B-l.1 As an example, a simple building with flat roof, 10 m x 20 m and 4 m high is dealt with below. For the sake of generalization, no shading device or verandah is taken.

El.2 As the roof is horizontal, it will receive the same solar heat in any orientation.

B-l.3 The areas of the vertical surfaces are 4 m x 10 m-A (say) and 4 m x 20 m=2 A. Since the external wall surfaces are not in shade except when the sun is not shining on them, the total solar load in a day on a surface can be obtained by multiplying the total load per unit area per day (Table 1) by the area of the surface. For four principal orientations of the building, the total solar load on the building is worked out in Table 2.

B-l.4 From Table 2 it can be seen that for the above type of building, orientation 3 (longer surfaces facing north and south) is appropriate as it affords maximum solar heat gain in winter and in summer. This is true for ~111 places of India from the point of solar heat gain. By further increasing the length to breadth ratio, the advantage of this orientation will be more pronounced. It may also be noted that in higher altitudes, the relative merit of this orientation is more.

B-l.5 It is also seen that the total solar heat on the building is the same for orientation 2 and 4. But if the site considerations require a choice between these two, at places north of latitude 23”N, orientation 2 should be preferred and orientation 4 at southern places. This is so, because, the total solar load per unit area in summer on the north western wall decreases with the increase in latitude and that on the south western wall increases. It would, therefore, be advantageous to face only the smaller surface of the building to greater solar load in the summer afternoons, when the air temperature, also, is higher.

16

TABLE 2 SOLAR HEAT GAINED DUE TO ORIENTATION OF BulLDINGS (Clali5~ El.3 and B1.4)

1 North

East

!3OUth WC?&

8”N TRIVANDRUM 13”N MADRAS 19”N BOMRAY L A * , , , >

May 16 Dee 22 May 16 Dee 22 May 16 De.c 22

187x A=187A - 140x A=14OA - 83xA=83A -

225 x 2A=450A 187 x 2A=374A 232 x 2A=464A 173 x 2A=346A 240x 2A=480A 157 x 2A=314A - 358x A=358A - 377x A=377A - 393x A=393A

225~2A=45OA 187~2A=374A 232~2A=464A 173xPA=346A 24Ox2Ad8OA l57x2A=314A

Total 1087A 1106A 1068A 1069A 1043A 1021A

2NE 228~ A=228A 35x A= 35A 214x A=214A 27x A= 27A 194x A= 194A 20x A= 20A

SE 100 x 2A=2OOA 291 x 2A=582A 115 x 2A=230A 294x 2A=588A 141 x 2A=282A 295 x,2A=59OA

SW 100x A=lOOA 291x A=291A 115x A=115A 294x A=294A 141x A=14lA 295x Ac295A NW 228x 2A=456A 35x2A= 70A 214~2A=428A 27x2A= 54A l94x2A=388A 2Ox2A= 4OA

Total 984A 978A 987A 963A 1005A 945A

3 North 187 x 2A=374A - 140 x 2A=280A - 83x2A=166A -

East 225x A=225A 187 x A=187A 232 x A=232A 173 x A=173A 240x AdbOA 157x A=157A

SoUtb - 358~2A=716A - 377 x 2A=754A - 393 x 2A=786A

West 225x A=225A 187x A= 187A 232 x A-232A 173x A=173A 240x A=24QA 157x A= 157A

Total 824A 109OA 744A 1 1OOA 646A 1 1OOA

4NE 228 x 2A=456A 35x2A= 70A 214x2A=428A 27x2A= 54A 194~2A=388A 2Ox2A= 4QA

SE 100x A=lOOA 291x A=291A 115x A=115A 294x A=294A 141x A=141A 295x A=295A

SW 100 x 2A=2OOA 291 x 2A=582A 115 x 2A=230A 294x 2A=588A 141 x 2A=282A 295 x 2A=59OA

NW 228x A=228A 35x A= 35A 214x A=214A 27x A= 27A 194x A-194A 20x A= 20A

Total 984A 978A 987A 963A 1 005A 945A

23”N &LCU’lTA 29”N DELHI * L I 1 I ,

May 16 De-c 22 May 16 Dee 22

1 North 64x A= 64A - 4iixA=46A -

EaPt 247 x 2A=494A 146x 2A=292A 253~2A=506A l26x2A=252A

South 18x A= 18A 398x A=398A 64x A= 64A 390x A=39OA

West 247 x 2A=494A 146x 2A=292A 253~2A=506A l26x2A=252A

Total

2NE

SE

SW

NW

Total

3 North

East

South

west

Total

4NE

SE

SW

NW

Total

1 07OA 982A 1 122A 894A *

188x A=188A 15x A= 15A 180x A=180A 9x A= 9A

158~2A=316A 297x2A=594A l88x2A=376A 28lx2A=562A

158x A=15&i 297x A=297A 188x A=188A 281x A==281A

188x 2A=376A 15x 2A= 30A 180x 2A=36OA 9x2A= 18A

1038A 936A 1 104A 870A

64x 2A=128A - 46x2A= 92A -

247x A=247A 146x A=l&A 253x A=253A 126x A-126A

18x2A= 36A 398~2A=796A 64 x 2A= 128A 390 x 2A=780A

247x A=247A 146x A=146A 253x A=253A 126x A-126A

658A 1088A 726A 1032A

188x 2A=376A l5x2A= 30A 18Ox2A=36OA 9x2A= 18A

158x A=158A 297x A=297A 188x A=188A 281x A=281A

l58x2A=316A 297x2A=594A l88x2A=376A 281~2A=562A

188x A=188A 15x A= 15A 180x A=18OA 9x A= 9A

1038A 936A 1104A 870A

ORXENTAT~ON

A

N

2A 0 f 2A

A

2A

A A

2A ti

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